1. Field of the Invention
The invention relates to a diode modulator for obtaining a line scanning with a line S-correction. The invention also relates to a picture display device comprising such a diode modulator.
2. Description of the Related Art
U.S. Pat. No. 5,666,033, corresponding to non-prepublished French patent application No. 9511035 filed on Sep. 20, 1995, (Attorneys docket PHF 95,557), describes a circuit for generating an acceptable line S-correction suitable at two mutually different line deflection amplitudes. This U.S. Patent application describes a diode modulator circuit which comprises an S-capacitor, an additional S-capacitance, and a thyristor. The thyristor activates or deactivates the additional S-capacitance for the purpose of correcting the S-correction of a television image having a 4/3 aspect ratio which is displayed on a picture screen having a 16/9 aspect ratio. In this way, it is possible to obtain an acceptable S-correction in the line direction at the two values of the line-scanning currents corresponding to the line scan widths at the 4/3 and the 16/9 aspect ratios, respectively.
The circuit described in the above U.S. Patent has the drawback that a lot of extra components are needed to obtain an acceptable S-correction at the two scan widths. This is expensive, and as these extra components are used in high-voltage and large-current surroundings, the reliability decreases. Moreover, the S-correction obtained is only optimal in the proximity of the 3/4 and 16/9 scan widths.